Broad band television antenna



June 21, 1960 J. GREEN 2,942,259

BROAD BAND TELEVISION ANTENNA Filed Oct. 3, 1956 5 Sheets-Sheet 1 IN VENTOR.

JZ/L/US GREEN BY A TTOEA/C'VS June 21, 1960 J. GREEN 2,942,259

. BROAD BAND TELEVISION ANTENNA Filed Oct. 3, 1956 5 Sheets-Sheet 2 INVEN TOR. JZ/L/us GREEN BY A TTOEA/EVJ' J. GREEN BROAD BAND TELEVISIONANTENNA June 21, 1960 5 Sheets-Sheet 3 Filed 001;. 3, 1956 j a 4 W r 2 aW 7 Z fi M 4 1 Z T WW 0 2 w 5 8 a W 4 lo 4 4 54 4 4 0/ 7O w v H i A a Qm 5 f 4 /o d 7 a 4 v 4 m/ 3 0 4/ a a fi uw 4 3 T z m 5 I? ll/W INVENTORJ UL/US GEL-"5N BY 8 g i A I ATmkA/Ey:

Jlme 21, 1960 J. GREEN 2,942,259

BROAD BAND TELEVISION ANTENNA Filed on. s, 1956 5 Sheets-Sheet 4 Tic. E

I il I o f 65 a /0 47 44 A? q 4a 47 INVENTOR.

J11 /us GREEN i Z Arron/Ev;

June 21 1960 J. GREEN 2,942,259

BROAD BAND TELEVISION ANTENNA Filed Oct. 3, 1956 5 Sheets-Sheet 5 Tia.13A.

IN V EN TOR. J14 /us GRN g i; RNEYS United States Patent 2,942,259 BROADBAND TELEVISION ANTENNA Julius Green, Ellenville, N.Y., assignor toChannel Master Corporation The present invention relates to televisionantennas adapted to receive both high-band and low-band televisionsignals and-more particularly to such antennas incorporating means fortuning the antenna to particular television channels.

Substantial difliculty has been encountered in designing a televisionantenna suitable for indoor use which is moderately compact and yetsatisfies the requirements for an'etlicien-t television antenna. Themost widely accepted indoor television antenna at the present time isthe Rabbit Ears antenna, utilizing a pair of telescoping arms ofadjustable length, inclined to the horizontal at .adjustable angles.Virtually all indoor antennas in use today are Rabbit Ears antennas ormodifications of the Rabbit Ears antennas. This antenna, however, hasnumerous inherent deficiencies which have not been satisfactorilyovercome by modifications, such as adding spiral coils, adding loops, orincorporating switching arrangements for tuning.

The Rabbit Ears antenna is basically a straight single dipole, which hasan impedance of about 72 ohms at resonance, and therefore the RabbitEars antenna is inherently mismatched to the conventional BOO-ohmtransmission line. In practice, the Rabbit Ears antenna is even moreseriously mismatched because its inipedance is often even less than 72ohms unless it is ca efully adjusted to one-half wavelength for theparticular there is a still further loss in antenna efiiciency.

Although most Rabbit Ears antennas are not sufficiently long to providea half-wavelength dipole at low VHF frequencies, their arms are still ofconsiderable length and hence the antennas are space-consuming andunsightly.

Rabbit Ears antennas are generally constructed so that the Earstelescope and hence .their length can be changed, ostensibly to tune,the antenna to the channel being received. In practice, however, the actof tuning the antenna "by adjusting the arm length loads the antenna'andtemporarily changes its characteristics so that it is virtuallyimpossible for the average viewer to determine the :correct length foroptimum reception.

The present invention provides a 'distinct departure from the RabbitEars antenna and modifications of the Rabbit Ea-rs antenna which arecommon inthe indoor antenna art. The present antenna isof fixed lengthand shape, and includes special means to function efliciently for boththe low-band VHF television channels (extending in frequency from 64 to88 megacycles) and Patented Juarez-1, 1960 the high-band VHF televisionchannels (extending in frequency from 174 to 216 megacyc'les).Furthermore applicants antenna incorporates a tuning mechanism toprovide optimum reception at any desired VHF television channel, thesame tunning mechanism being useful both on low-band and on high-bandoperation, although operating on different principles for the two bands.The tunability feature also serves to reject interference at otherfrequencies. The tuning mechanism of the present invention does notrequire changes in the antenna length or size or shape but isaccomplished merely by turning a tuning knob to the desired channelnumber. In spite of the high degree of efiiciency on both high-band andlow-bandtelevision channels, an antenna according to the presentinvention may be made very small compared ,to the ordinary Rabbit Ears"antenna.

It is therefore an object of the present invention to provide an indoortelevision antenna adapted to elliciently receive television signals inboth a high frequency band and a low frequency band.

It is another object of the present invention to provide a high band-lowband antenna in which the largest dimension of the antenna is smallcompared with the length of a half-wave dipole antenna for the lowfrequency band.

It is another object of the present invention to provide an indoor VHFtelevision antenna which may be tuned to particular television channelsfor maximum eifectiveness.

It is still another object of the present invention to provide an indoortelevision antenna which may readily be rotated upon its base in orderto orient the antenna for best reception from a particular station. 7

It is a further object of the present invention to provide an indoor VHFtelevision antenna which is of light weight'and of attractive appearanceand which may be disassembled and folded so that it occupies a verysmall volume and thus may readily be stored and transported.

Other objects and advantages of the present invention will be apparentfrom a consideration of the following description in conjunction withthe appended drawings, in which Fig. 1 is a top plan view of an indoortelevision antenna according to the present invention partially cut awayto show the internal construction of the cap at the right extremity ofthe antenna as viewed in the figure;

Fig. 2 is a front elevational view of the antenna shown in Fig. 1;

Fig. 3 is a side elevational view of the antenna shown in Fig. 1; I

Fig. 4 is a fragmentary perspective view of one end of the antennashowing an alternative construction for the end-hat structure of theantenna;

Fig. 5 is a vertical sectional view of the antenna show ing thealternative end-hat of Fig. 4;

Fig. 6 is a fragmentary top plan view of the antennae showing thealternative end hat of Fig. 4.

Fig. 7 is a fragmentary horizontal sectional View of the central housingof the antenna shown inFig. ,1;

Fig. 8 is a vertical sectional view of the central antenna housing takenalong the line 8-8 in Fig. 7; a

Fig. 9 is a fragmentary vertical sectional view of the central housingtaken along the line 9-9 in Fig. 7;

Fig. 10 is a fragmentary vertical sectional view of the tuning assemblytaken along the line lid-10 in Fig. 7

Fig. 11 is a fragmentary vertical sectional-view .of the tuning coiltaken along the line 11--,11 in Fig. 10;

Fig. 1.2 is a'fragmentary vertical sectional view .of thetuning'drivehelix taken along the line 12-12 in Fig. 10;

Fig. 13a is a schematic circuit diagram of the-electrical circuit of theantenna shown in Fig. 1;

and 7-9, an antenna base 10 is provided to support the I antenna. Theantenna base 10 has three legs 11 forming a tripod support for theantenna. If desired, the legs 11 may be provided with protective caps 12which may be of rubber, plastic or some similar material and serve toprotect the surface of a piece of furniture or the like upon which theantenna may be placed.

A tuner housing 14 is pivotally mounted on the antenna base 10. Thetuner housing 14 is provided with a front panel 15 on which is mounted arotatable tuning knob 16. The tuning knob 16 is aflixed to a shaft 17extending into the interior of the tuner housing 14. On the front of thetuner knob 16 there is provided an outer dial 19 and an inner dial 18.The channel numbers of the television channels in the high band areplaced on the outer dial 19 while the channelnumbers of the televisionchannels in the low band are placed on the inner dial 18, at appropriatepoints determined in the manner indicated below. An indicator arrow orindex 22 is provided at the top of the housing 14 which cooperates withthe numbers on the dials 18 and 19 to indicate the television channelsto which the tuner is set. A suitable transmission line 23 extends outthe bottom of the tuner housing 14 and throughthe open center of theantenna base 10 for connection to the televisoin receiver.

A low-band antenna rod 24 extends outwardly from each side of the tunerhousing 14. Two high-band antenna rods 25 extend outwardly from thehousing 14 on either side of and parallel to each of the low band rods24 and in the same horizontal plane therewith. The rods 24 and 25 areconstructed of a conductive material and in the preferred constructionshown in the drawings, the center or low-band rod 24 has a slightlygreater diameter (for example, 3A diam.) than the high-bandrods 25 (forexample, A" diam.). In another form, the rods may be of equal diameter,say W The diameters of the rods 24 and 25 are not particularly criticalbut should be large enough to provide a rigid structure for the antenna.The length from tip to tip in the preferred construction shown in thedrawings is approximately 19" for the high-band rods 25 andapproximately 21" for the low-band antenna rods 24.

Thus it will be seen that, with an overall length of less than 2 feet,the antenna shown provides a very compact structure. The physicallengths of television .dipole antenna rods are invariably somewhatcritical unless compensated electrically, and such is the case with anantenna according to the present invention. However, the antenna shownincludes a tuning inductance which will subsequently be described, andhence an adjustment of the value of the inductance in the tuningassembly is made to compensate for substantial variations in theeffective electrical lengths of the antenna rods from channel tochannel. It is believed, however, that the constuction and dimensionsdescribed are preferable from the standpoint of compactness andefficiency.

Attached to the ends of the antenna rods 24 and 25 are respective caps26. The caps are of non-conductive material and each is provided attheir inmost edges with holes 27 for the entrance of the high-band rods25 and a hole 28 for the entrance of the respective low-band rod 24. Thecaps 26 are constructed of an upper cap section 26a and a lower capsection 26b which are fastened together by means of bolts 30 or by othersuitable fasteners. The lower cap sections 26b, as shown in Fig. 1

.are provided with webs 29 against which the high band rods 25 abut fordetermining the position of the caps 26 4 on the ends of the rods 24 and25. These webs 29 also prevent accidental electrical connection betweenrods 25 and other parts of the system.

End hats 31 are provided at the ends of the antenna rods 24 and 25 andare secured thereto by means of the cap 26. The end hat 31 isconstructed of a rectangular vertical closed loop 33 of conductivematerial and a horizontal triangular brace member 32 interrupted at itsinner vertex and with its other vertices secured respectively to thecenters of the short sides of the loop member 32. The end hats 31 may beconstructed of any conductive material and are preferably constructed ofa material similar to that used for the rods 24 In the particularantenna shown the end hats are from five to six inches by 10 to 12inches. However, the dimension of the end hats is less critical than theantenna roddimensions.

It should be understood that the function of the end hats 31 is toprovide a conductive structure of substantial area at the ends of andconnected to the rods 24 to provide an end loading capacitive impedancefor the lowband antenna. The effect of such a structure is to pro videan increase in the effective length of an antenna rod 24 to which it iselectrically connected.

The end hat 31 is physically secured to the cap 26 by means of holes 34through which the brace members 32 pass and by means of a notch 35a inthe upper cap member 26a and a slot 35b in lower cap member 261) so thatthe ends of the brace member 32 may be secured between the cap members26a and 26b. The slot 35b allows the ends 32a of brace 32 to bedisengaged from cap 26 so that end hat 31 may be folded by pivoting itabout the holes 34 in the cap 26. The end hat 31 may thus be folded fromits operative vertical position to a horizontal position whereby theantenna is more nearly flat and occupies a lesser volume and may be morereadily stored and transported.

Figs. 4, 5 and 6 show an alternative construction for the end hat 31. InFig. 4 the end hat 31 is constructed of two identical frame sectionswhich are so shaped that each forms a half of the end hat. Each framesection 80 has a loop portion 81 having a long side 82 and two shortsides 83 and 84.

A brace portion 85 is adapted to retain the loop in position withrespect to a cap member 26. The brace portion 85 has a short section 86in the plane of the loop and joining it to section 83. The brace portion85 is bent at an angle to the plane of the loop, and is in a planeperpendicular to the short sides 83 and 84.

The end of the brace 85 is adapted to fit in a slot 35b in the end cap26 in a manner similar to that shown in Figs. 1-3.

Half of the central cross piece of end hat 31 is formed by the centersection 87. This center section 87 is bent at a right angle to the side84 and lies in the plane of the loop. An offset portion 88 is providedat the outer end of the center section 87 which is of a length somewhatlonger than the joining section 86. When two of the mating framesections 81 are placed together as shown, the joining section 86 of thefirst lies adjacent the offset 88 of the second and vice versa.

Thus two of the frame sections 81 may be welded or otherwise fastenedtogether at 89 where the offset and joining sections adjoin to form anend hat 31' as shown in Figs. 4-6. The shape of the frames 80 is suchthat an end hat 31' is formed which is substantially the same shape asthe end hat 31 shown in Figs. l-3.

An obvious advantage accrues by constructing the end hat of twoidentical rather than two different parts since the number of differentparts required is reduced and hence theproduction cost is reduced. Inaddition only two welds are required in the construction shown in Fig. 4and the length along which the weld is made is increased to provide asturdier construction. Preferably the hats have a maximum dimensionapproximately equal toogsli'ghtly' less. than the length of one of therods 24 or The end hats 31 or 31' are not electrically connected to thehigh-band rods 25 due to the insulating properties of the webs 29' ofcap 25. The end hats 31 or 31 are, however; electrically connected tothe center low-band rod 24 bymeans of a contact or clip 36. (Fig. l.)which is press-fitted" over the outer. end of low-band rod. 24 and isof, resilient conductive material so that it presses against, the bracemember 32 (or 87 in the alternative embodiment) and thereby provides anelectrical connection between the center of each end hat and thelowbandirod.

As previously explained the end hat 31 serves as an end loadingstructurefor the low-band antenna system. Although particular types of endhatstructures are shown, it should be understood that any equivalentend-loading structure couldibe provided to serve to increase theefiective or electrical length of low-band antenna rods. 24 and", lowerthe frequency at which the low-band antenna system hasthe. desired.frequency-impedance. characteri'st-ics.

The inner connections of the antenna rods 24 and 25 in. housing. 14.are. shown in Fig. 7.. Thehigh-band. rods Ziare-formedof asingle rodbent generally in the shape of a, U. Anoifset 37 is. provided at thebase of the U for attaching: the high-band rods in the central housing14. by means. of rivets 38. passing through holesin columns. 39 formedasanintegral part of the lower portion 1421 of central housing 14;

Webs 41- having slots- 42 are provided to secure the low-band rods 24 inthe central housing 14. A bridge member 43 passesrover each low-band rod24 and is secured. in the slots 42. In some forms of constructionthis,.bridge member 43 may be omitted. The high-band rods 25.pass1: overthejends of bridges 43 and hence retain. bridges tTa; andthe rods 24 inplace. The ends 40 of the low-band rods 24 are bent, upward and outwardas seen most clearly in Fig. 8 to provide. a separationbetween'thevlowband rod and the high-band rod ends and. avoidundesirableelectrical coupling.

The. tuner mechanism is contained in a tuner housing 44. The rear endofthe tuner housing 44 is provided with L-shaped projections- 45 which.are engaged by; the. tunerhousing bracket 47" forsupporting the rear endof the tuner housing 44. Projections 46 on the front endof: the-tunerhousing 44 rest on a front bracket es thereby supporting; the frontendofthe tuner housing 44. Acylinder- 49-iir the front. part of" the tunerhousing 44 is provided to'retainthe tuningcam 51 (seen in Fig. 10).Thetuningcam 51 is connected to the tuner knob shaft 1-7-whichis inturn'connected to the tuner knob 16. R- tation' of; the tuning knob 16-therefore causes a corresponding rotation: of the tuning cam 51.

A- helicali web- 52 encircles. and is preferably molded integrally withthe tuning cam 51. A core-sliding bar 54 extends lengthwise in the tunerhousing 44 and is slidably retained in thebar slot 53 formed in therearward portion of tuner housing 44. A pair of projections 55 extendingdownward from the front end of the tuning bar 53 engage either side ofthe helical web 53 on the tuning cam 51, being spaced from one anotherin an axial direction;

ThllSwflSlhE tuning knob 16 and the tuning cam 51 are rotated, thehelical web 52 causes a translatory movement of the tuning bar 54. Thetuning bar 54 is provided with aforward projection 56 and a rearprojection. 7;. Between these forward and rear projections, fourtuningrcores 58a, 59a, 58b, and 5% are slidably retained: in a.cylindrical core. chamber 61 Within tuner housing 44R Bhcircling. thecore chamber 61 are two wire: coils 62;.

' The'cores58a and-58b vareof magnetic material whereas, the: cores 59aand 591i are. of nonmagnetic. conductive material, such as aluminum;Thus, as the magnetic cores 5% are slid into the-coils 62, theinductances of the coils 62 are increased, and as the cores 59 are movedinto the coils 62 replacing the cores 58, the coil inductanc'es aredecreased;

From the foregoing description, it may be seen that as the knob 16 isturned in a clockwise direction the tuning bar 54 is moved forward (tothe right in Fig. 10). The projections 57 and 56 engage the cores 58 and59 so that a corresponding movement of the cores is produced by themovement of the tuning bar 54. As the cores are moved to the right, themagneticrcores 58 are moved into the coils 62 and at the same time thenonmagnetic cores 59 are slid out of the coils 62. Thus a clockwisemovement of the tuning knob 16 causes the insertion of magnetic cores 58into the tuning coils 62 and removal of the conductive cores 59 from thecoils 62 and hence causes an increase in the inductive reactance of thecoils 62. This causes the antenna to be tuned to lower frequencies aswill later be explained. Conversely a counter-clockwise move of thetuning knob 16 causes a decrease in coil inductive reactances and aconsequent increase in the resonant frequency of the antenna.

Fig. 9 also shows the pivotal connection of the housing 14 on the base=10. The housing 14 has an annular shoulder 65' which rests on anannular plate 66 which forms the top of the tripod base 10. Acylindrical projection 64 on the bottom of the housing 14 fits withinthe opening in the annular plate 66. Latch sections 67 are provided inthe cylindrical projection 64 which are resilient and have recesses 68for permitting grasping the latch sections 67 to press them inward forrelease. Facing outward-on each latch section 67 is a projection 69which engages a recess 71 in the base 10 and thus holds the base 19 andhousing 14 together. The housing '16 is thus free to rotate on the base10 and may be removed from the base 16 for packaging or storing byinserting the thumb and forefinger in the recesses 68 and pressing thelatch sections 67 inward to release them from the base cylinder 64. i

The approximate equivalent electrical circuit of the antenna is shown inFig. 13A. The two high-band rods extending to each side of the antennaare shown at 25. The low band rods are shown at 24, with the end hats 31attached at their outer ends. Each pair of the highband rods 25 iselectrically joined together at their inner ends,and the junction isconnected by means of respective oneof the variable inductances 62 tothe inner end of'the corresponding low-band rod 24. Each joined pair ofinner ends of the high-band rods 25 is connected to a respectivetapon anautotransformer 50 also shown in Figs. 7 and9. The end terminals 63 ofthe autotransformer 50 are adapted to be connected to transmission line23.

Explanation of the operation of the antenna is facilitated byconsidering the antenna to be composed of two parts: a high-band sectionshown in Fig. 133 and a low-band section shown in Fig. 130. Thehigh-band section consists essentially of a high-band dipole each arm ofwhich is formed by a pair of parallel rods 25, and which is connected toan impedance-transforming autotransformer 63. It should be understoodthat an equivalent imped'ance-transforming device could be used in placeof the autotransformer 50 shown in the preferred construction.

The low-band section of the antenna as shown in Fig. 13C consists of adipole having arms 24 with end hats 31 and variable center-loadingseries inductances 62. The low-band section of the antenna is connectedto the same taps on the autotransformer St or, in other words, isconnected in parallel with the high-band section shown inFig. 12B.

Since the high-band and the low-band sections are connected inparallel,they obviously have an influence upon each other. However, due to therather short length of the rods 25 compared to a quarter-wave length atfrequencies in the low-band, the high-band section has relatively littleinfluence upon the low-band section" when operating on low-bandchannels. The reverse is not correct; the operation of the high-bandsection at high band frequencies is definitely affected by the fact thatthe lowband antenna is effectively connected in parallel, and thiseffect is utilized here, as is shown below.

Considering first low-band operation (and ignoring the high-band sectionas having relatively little effect), it will be seen that the rods 24are considerably shorter than required for a tuned simple dipole at anylowband channel. As a result, a dipole formed of arms 24 alone wouldhave a substantial capacitive reactance but a low radiation resistanceof the order of 3 ohms, a far cry from the desired matchingline-impedance of 300 ohms. The hats 31 provide end-loading whichincreases the effective length of the antenna and increases itsresistance to the order of 30 ohms, but leaves the impedance highlycapacitive. The hats actually do not receive radiation because theirfront and rear halves have opposite and cancelling induced currents. Theseries inductances 62 serve to compensate for the effective capacitanceof the arm plus hats. The inductances 62 are variable to provide meansfor-tuning the antenna to the various low-band channels in the preferredconstruction shown. It should be understood that tunability is a highlydesirable, but is not a necessary feature of certain aspects of theinvention where approximate impedance-matching can be tolerated.

The particular means for adjusting the inductances is of special utilityhere because it provides the desired wide variation in inductance (bothabove and below that of the coils with cores removed) with relativelysmall adjustment.

In this way, the antenna for each low-band channel appears as a pureresistance of about 30 ohms. (The high-band section merely adds acertain amount of capacitance, which joins as part of the totalcapacitance compensated by the coils 62.) This 30-ohm value is raised tothe required 30-ohm value by the autotransformer 50. In some cases itmay be desirable that the transformed impedance value be less than 300ohms (say, about 200 ohms) to provide greater band width and moreuniform frequency characteristics over each channel band.

It is important to note that the use of end-loading hats also solves theimportant problem of band-width. With a low radiation resistance of 3 or4 ohms, the dipole could not be closely enough resonated over asufficient band-width to cover even a single channel, and a step-upratio of 100 to l for the autotransformer would then prevent uniformstepped-up impedance over the channel width. However, the hats avoidthese difficulties (especially crucial for color television) byincreasing the natural radiation resistance and by reducing the requiredstep-up ratio.

According to an important feature of this invention, the foregoingsolution to lowaband reception was given, while permitting use of thesame tuning apparatus on high-band channels.

On high-band operation, the low band'section represents an impedance inparallel with the high-band dipole formed by rods 25. Because of thehighly successful solution for low-band operation, the low-band dipolearms 24 could be considerably shorter than those for the shortesthalf-wave high-band dipole, so that the high-band arms 25 are alsoshorter than for such a halfwave dipole, and offer a capacitiveimpedance over the entire high-band. This capacitive impedance can betuned by adjusting the same tuning mechanism so that the low-bandsection presents an effective inductance resonating with the high-bandsection. in order that the same autotransformer may be used, theradiation resistance of the high-band section on. high-band channels isselected to have the proper value, and a flat frequency response isattained, by having each high-band arm in the form of parallel rods 25forming a U, simulating a flat dipole having fiat frequency response.

Thus the same tuner and autotransformer are utilized for both low andhigh band operation. The tuner knob 16 therefore has two concentricdials, respectively'calibrated for low-band and high-band channels, sothat in each case, positioning of knob 16 so that the received channelnumber is opposite the index mark, will set the variable inductances tothe proper value regardless of which band is being received.

Thus a desirable effect of the parallel connection of low and high-bandsections accrues from the factv that the high-bandsection may be tunedby varying the same inductances 62 and hence varying the total impedanceconnected in parallel with the high-band section.

Another advantage of the parallel connection resides in the fact thatthe high-band antenna may be constructed of a length shorter than anordinary tuned high-band half-wave dipole by reason of the fact that thelow-band section and the associated inductances 62 are connected inparallel with the high band section, permitting smaller overall size ofantenna.

Where still shorter overall dimensions are desired, the arrangement ofFig. 14 may be used, where clip 36a has extensions approximately oneinch long parallel to and spaced from rods 25 by dielectric spacingwalls 36b, thus providing extra capacitance for rods 25 effectivesubstantially only in the high-band, With this arrangement, the overalllength of the antenna may be of the order of 19 inches; with rods 25approximately the same length as rods 24.

In the preferred construction of the low-band highband antenna shown anddescribed, it is obvious that there will be some interaction between thehigh-band and low-band dipoles due to the close association of rods 24and 25. The particular arrangement shown makes use of the effect of suchinteraction, and assures that it does not adversely affect the antennaoperation.

- It will be understood that the autotransformer 50 may have differentcharacteristics at different frequencies or hands. This is immaterial inthe present invention, since such variations can generally becompensated by proper adjustment of the variable inductances. In somelowimpedance antenna applications, the autotransformer may be omrnittedentirely.

It will also be understood that while the particularinductance'adjusting means herein disclosed is of special advantage,because of its simplicity, economy, and wide range, other such means maybe used if desired.

It is known that the design of antennas is often accomplished withoutfull knowledge of the precise theory of operation which is responsiblefor the beneficial results obtained. Therefore, it should be understoodthat the description of the theory of operation of the presentinvention, although believed correct, is not intended to be of alimiting nature.

Although a particular embodiment of the invention has been shown anddescribed, it should be understood that a person skilled in the artmight make many modifications to the device within the scope of thepresent invention, and hence the embodiment shown and described is notto be taken in a limiting sense, but rather the scope of the inventionis to be limited solely by the appended claims.

What is claimed is:

l. A compact dual-band antenna operable on high and low bands comprisinga first dipole having arms shorter than required for resonance at everyfrequency in said high band, whereby said first dipole presents acapacitive impedance throughout said high band; a second dipole havingarms parallel and closely spaced to not more than one-eighth wavelengthof the maximum antenna frequency from said first dipole arms; capaci- 9r tive 'endJpading means for said second dipole; (IDQIRX'iS? ingrespectiye, conductive structures 'at; tl ie ends ofsai'cl first dipolearms, and means'operative to tune. said antenna to frequencies in bothsaid h gh. and said low bands, comprising a pair ofadjustable-inductance coils each connected betweemafirst dipole-aarminner end and a corr spond ng: e ond d po ealm nner. end, wh re y whenviewed at the said first dipeleiarm innenends-said.

coils may tune said second dipole andend-loading means to frequencies insaid low band and may incombination with said second dipole andend-loading means present a parallel inductance tuning said first dipoleto frequencies in said high band.

2. A multi-band antenna suitable for television reception on low andhigh frequency bands where said high band has frequencies substantiallyhigher than said low band comprising a high-band dipole operative atfrequencies in the high band, a low-band dipole in parallel relation toand spaced not more than one-eighth wavelength of the maximum antennafrequency from said high-band dipole, a conductive end-loading structureat each end of said high-band dipole, said structure being conductivelyconnected to said low band dipole and not directly in electrical contactwith the outer end of said high band dipole, means for electricallyconnecting said dipoles in parallel, and means for connecting atransmission line to said parallel connected dipoles, whereby saidantenna has desirable impedance-frequency characteristics at both thelow frequency band and the high frequency band.

3. An antenna as claimed in claim 2, further including an inductivereactance element in series with each arm of said low-band dipole forcausing said antenna to be resonant at frequencies in the low band aswell as in the high band.

4. An antenna as claimed in claim 3, further including means foradjusting said reactance element to tune said antenna to differentfrequencies in both said bands.

5. An antenna as claimed in claim 2, wherein said means for connecting atransmission line comprises an impedance-transforming element forsubstantially matching the antenna impedance to the characteristicimpedance of a transmission line.

6. A'dual-band television antenna comprising a highband dipole havingarms shorter than required for reso nance at frequencies in the high VHFtelevision band, a low-banddipole having arms in close spaced parallelrelation thereto, a conductive end-loading structure at each end of saidhigh-band dipole, said structure being conductively connected to saidlow-band dipole and not directly in electrical contact with the outerend of said high-band dipole, a respective inductance electricallyconnected in series with each arm of said low-band dipole, said seriescombination of low-band dipole and inductances being electricallyconnected in parallel with said high-band dipole, impedance-matchingmeans connected to said parallel-connected dipoles and includingterminals for connecting a transmission line to said antenna, whereby anantenna is provided operable in both the low VHF television band and thehigh VHF television band.

7. A dual-band television antenna as claimed in claim .6, furtherincluding means for adjusting said inductances television channel fre-110 pposit sid s of. said support, said" rods; bein of. a length. lessthan that required to form a half-wave dipole resonant in saidhigh-band, a respective low-band rod extending fronwaid up ort parallelspaced: relation to an between each; pair ofhigh-band rods, a.respective endloading; structure conductively connected toeachsaidlowband rod f'on causing said low-band, rod: to beresonant at;a. lower. frequency than without said structures, means for electricallyconnecting the inner ends of each pair of parallel-high-band rods, aninductive coil connected between the inner termination of each saidlow-band rod and the electrical junction of its corresponding pair ofhigh-band rods, means for adjusting the inductance of said coils fortuning said antenna to different frequencies in each said band and meansfor coupling a transmission line to the electrical junctions of saidhigh-band rods whereby said antenna is provided with parallel connectedhigh and low-band sections.

11. A television antenna as claimed in claim 10, wherein each saidend-loading structure comprises a loop of conductive material having aconductive cross member, said cross member being connected to arespective low-band rod at a point substantially at the center of saidloop.

12. A television antenna as claimed in claim 11, wherein said loop issubstantially rectangular.

l3. A television antenna as claimed in claim 11, wherein said loop has amaximum dimension approximately half the tip to tip length of saidhigh-band rods.

14. A dipole antenna comprising a pair of aligned rods, an insulatingmounting at the end of each arm, a pair of rigid closed planar loops ofconductive material, a conductive cross-member extending across eachsaid loop, and means securing each said cross-member on a respective oneof said mountings with its center in electrical connection with thecorresponding rod, said loop planes being perpendicular to said rodssaid mounting supporting said loops with respect to said rods withportions of said loops out of direct electrical contact with said rods.

15. An antenna as in claim 14 wherein each said loop, and cross-memberare formed from two identical-shaped rods joined together.

16. In a multi-band antenna suitable for television reception on low andhigh frequency bands where said highband has frequencies substantiallyhigher than said lowband, said antenna having a high-band dipole havingtwo arms, a low-band dipole, a conductive end-loading structure at theend of each of said high-band dipole arms and conductively connected tosaid low-band dipole, the improvement comprising means for capacitivelycoupling each arm of said high-band dipole to a corresponding endloadingstructure, said capacitive coupling means comprising a spacer of soliddielectric material placed between a portion of each said high-banddipole arm and an adjacent part of the corresponding end-loadingstructure.

17. A m-ulti-band antenna suitable for television reception on low andhigh frequency bands where said highband has frequencies substantiallyhigher than said lowband, comprising a high-band dipole having two arms,a low-band dipole having two arms, an adjustable reactance elementcoupling each inner end of said high-band dipole arm to a respectiveinner end of the corresponding lowband dipole arm, and output terminalscoupled to the inner ends of said high-band dipole arms, whereby saidlow-band dipole may be tuned by adjustment of said reactanceseffectively in series therewith and said high-band dipole is tunable bythe series combination of said adjustable reactances and low-band dipolearms which together are efiectively in parallel with said high-banddipole, said high-band dipole being in parallel relationship to saidlow-band dipole and spaced therefrom not more than one-eighth wavelengthat the maximum antenna frequency.

18. An antenna as claimed in claim 17 wherein each said adjustablereactance is an adjustable inductance.

19. An antenna as claimed in claim 17 including means 2,281,429mechanically coupling said adjustable reactances for si- 2,558,145multaneous adjustment. 2,611,086

2,640,933 References Cited 1n the file of this patent 5 2 686 873 UNITEDSTATES PATENTS 930,746 Eisenstein Aug. 10, 1909 1,868,795 Hansell July26, 1932 2,048,726 Bohm July 26, 1936 12 Goddard Apr. 28, 1942 Mock June26, 1951 Amy et a1. Sept. 16, 1952 Spindler June 2, 1953 VilkomersonAug. 17, 1954 OTHER REFERENCES Zaun: Abstract of application SerialNumber 64,582, V published I an. 8, 1952, 0.6.

